Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known is the type of alcohol found in alcoholic beverages, but it is also used as a solvent, and as fuel oxygenate for gasolines, biofuels and biodiesel.
Ethanol has widespread use as a solvent of substances intended for human contact or consumption, including scents, flavorings, colorings, and medicines. In chemistry, it is both an essential solvent and a feedstock for the synthesis of other products. It has a long history as a fuel for heat and light, and more recently as an additive to fuel for internal combustion engines intended to reduce airborne pollutants.
The fermentation of sugar into ethanol is one of the earliest organic reactions employed by humanity. The intoxicating effects of ethanol consumption have been known since ancient times. The process of culturing yeast under conditions to produce alcohol is called fermentation. This process is typically carried out at temperatures of around 35-40° C. The toxicity of ethanol to yeast limits the ethanol concentration obtainable by brewing. The most ethanol-tolerant strains of yeast can survive up to approximately 15% ethanol by volume. To produce ethanol from starchy materials such as cereal grains, the starch must first be converted into sugars. In brewing beer, this has traditionally been accomplished by allowing the grain to germinate, or malt, which produces the enzyme amylase. When the malted grain is mashed, the amylase converts the remaining starches into sugars. For fuel ethanol, the hydrolysis of starch into glucose can be accomplished more rapidly by treatment with dilute sulfuric acid, fungally-produced amylase, or some combination of the two. Cellulosic ethanol follows the same pathway, but requires steam and enzyme pre-treatment of the undigestible lignocelluloses.
Congeners are objectionable chemicals that are formed during fermentation. Some beverages have more congeners than others. In drinking alcohol, particularly in darkly colored liquors such as beer, wine, rum and cordials, these congeners are responsible for headaches and hangovers, but they also add taste and aroma to the liquors.
Complex organic molecules such as acetaldehyde, formaldehyde, methanol and acetone are found in some alcoholic beverages and are said to be principally responsible for hangovers, in addition to the ethanol itself. Manufacturers (distillers) of adult beverages have for years strived to remove congeners from drinking alcohol because of their metabolic impacts and off-flavors and odors. However, the processes utilized for this purpose, such as distillation, oxidation, low- or high-frequency cavitation and the like, are energy consuming and also tend to remove significant quantities of ethanol, venting toxic and otherwise objectionable compounds into the atmosphere. As much as 30% of beverage ethanol is lost with the requirement of multiple distillation steps to remove congeners for a high end vodka, for example. The system is also demonstrated to be capable of removing polyaromatic (i.e., naphthalene and phenanthroline-like) residuals from activated carbon treatment of vodka, bourbon whiskey, scotch and other beverages.
Congeners also pose considerable challenges for makers of corn or grain ethanol. Fusel oils (mixtures of higher alcohols such as propyl, butyl, and amyl alcohols and their isomers) can be very difficult to remove from the azeotrope. The uncontrolled release of volatile fermentation by-products such as acetaldehyde results in millions of dollars in fines yearly for ethanol distillers. In addition, the congeners irreversibly foul the zeolite molecular sieves used to dry 190 proof ethanol for use in fuels, resulting in high maintenance cycle costs. Removal of these contaminant congeners prior to drying will dramatically reduce costs for zeolite replacement, minimize waste disposal expense and improve product quality. Congeners not removed during distillation and left in the “backset”, the product water returned to the mash, can be toxic to yeast. Finally, congeners which are not removed during distillation are burned in the internal combustion engine when 200 proof dried ethanol is used as an oxygenate, possibly being converted to more toxic products as air pollution or exhausted unchanged as urban air pollution.
Extensions of the technology will include ultraviolet radiative treatment, which produces large numbers of free radicals and will treat multi-ring and polyphenolic compounds and tannins in darker spirits, electrokinetic treatment effecting oxidation/reduction reactions and radiofrequency treatment for dis-agglomeration, de-emulsification and de-stabilization. Large scale energetic reactors employing various technical means of delivering energy may be employed, including flow-through and re-circulating designs.